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Old 09-12-2019, 02:15 PM   #1
Dunk
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Default 78-8620 'A' vs 'C' gen belt 42-48

Several older forums addressed this with no solution. My '48 Merc is restored factory original (990+ Dearborne Award) - with the 3-3/16 gen pulley. It has a 78-8620 'A' belt with white Ford markings that I put on in 1999 from Mac's. I ordered what Drake lists as 78-8620 belt for 42-48 car and 41-47 truck - which came as a 'C' suffix - twice. It is wider (won't slip between fan and radiator) and is a 1" to 1-1/2" too short. No way will it fit. Older forums visited suggest that Ford changed gen pulley in June '40 or '41 from 3-11/16 to 3-3/16 which is what I have, so it ain't da pulley. Supplier says that Drake once offered the 'A' belt but later examples were too short so they stopped offering it and just sell the 'C' which DOES NOT FIT. I wrote to Drake but no response. All I want is a 78-8620 belt to fit a factory correct 1948 Mercury, with Ford script. Why is that so hard?
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Old 09-12-2019, 02:28 PM   #2
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Default Re: 78-8620 'A' vs 'C' gen belt 42-48

Its been quite awhile since I was in the power transmission section of the industrial business BUT A "C"section belt is a Heavier duty belt than an "A" section....maybe this link will help you understand. https://www.powertransmission.com/ar...d_Replacement/
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Old 09-12-2019, 05:40 PM   #3
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Default Re: 78-8620 'A' vs 'C' gen belt 42-48

Robert,


The suffix refers to Ford's design level of the part, not to an industry reference as to a cross section size.
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Old 09-13-2019, 10:18 AM   #4
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Default Re: 78-8620 'A' vs 'C' gen belt 42-48

Good to know the engineering stats and thanks, but all I want is to send a reputable supplier some $$$ and get a correct Ford Script belt that will fit my factory original '48. Can't believe that with all the 42-48 production flatheads running around that a correct Ford generator belt that fits isn't available - regardless of suffix letter. I checked this Drake 'C' belt on three other 47-48 cars and it was too short on two of them (identical non-fit as on mine) and couldn't get it between the fan and radiator on the other..... Can buy generics all day for $6 to $10 - at issue is a 'correct' Ford Scrip belt, and $30 to $50 for a Drake 78-8620 C is money wasted. Drake has long provided high quality correct stuff and I appreciate them for doing so..... but if they know about this, they ain't saying since they won't respond to my polite request.
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Old 09-13-2019, 10:28 AM   #5
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Default Re: 78-8620 'A' vs 'C' gen belt 42-48

Find a belt that works and get a stamp set made to reproduce the markings. In other words, you'll have to find a way to make a reasonable clone using what you have at hand. It seems no one else out there is willing to do it. I've seen this type of stuff done before by resto shops.

Carpenter started his business by casting plastic knobs and Snyder started out by fabricating his own seat spring assemblies and that's just two examples of what I'm referring to.
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Old 09-13-2019, 11:25 AM   #6
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Default Re: 78-8620 'A' vs 'C' gen belt 42-48

I've done that previously and you make a good point. Just seems to me that somewhere out there is a commercially available repro Script belt that will fit.
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Old 09-13-2019, 11:41 AM   #7
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Default Re: 78-8620 'A' vs 'C' gen belt 42-48

With respect, what you are seeking was never available in reproduction form. Ford belts of the period were not stenciled with the Ford script and part number, but rather those were molded into the outside surface of the belt. What rotorwrench suggests is as close as you will get short of finding a NOS belt (which aren't that rare).
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Old 09-13-2019, 11:49 AM   #8
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Default Re: 78-8620 'A' vs 'C' gen belt 42-48

Well, that's of interest. The repro Drake 'C' is molded. My older Script was white stenciled. Since the Drake 'C' absolutely will not fit what it is advertised to fit, your idea of a stencil on a modern 'spec similar' belt is what I suppose I will have to live with. I'll put the 'A' back on, use the 'aftermarket' as a spare and spend my time and effort on other things -that matter. Appreciate reply.
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Old 09-13-2019, 02:24 PM   #9
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Default Re: 78-8620 'A' vs 'C' gen belt 42-48

Quote:
Originally Posted by Dunk View Post
Well, that's of interest. The repro Drake 'C' is molded. My older Script was white stenciled. Since the Drake 'C' absolutely will not fit what it is advertised to fit, your idea of a stencil on a modern 'spec similar' belt is what I suppose I will have to live with. I'll put the 'A' back on, use the 'aftermarket' as a spare and spend my time and effort on other things -that matter. Appreciate reply.
You can put the A back on but that won't be correct either.
Fan Belts for 85 and 95 H.P. Engines

Two different fan belts were installed on 1940 Ford passenger vehicles with 85 and 95 horsepower engines. Belt (78-8620-A) was installed only on vehicles whose generator pulleys were 3 11/16" in diameter. This belt / pulley combination was in production until the beginning of June, 1940. At that time a redesigned pulley with a diameter of 3 3/16" was placed in production. Thus a shorter belt (78-8620-C) was required and placed in production to coincide with the smaller pulley.

Fan Belts for 60 H.P. Engines

Two different fan belts were installed on 1940 Ford passenger vehicles with 60 horsepower engines. Belt (52-8620-C) was used only with the larger diameter generator pulley. When the smaller diameter generator pulley was placed in production at the beginning of June, 1940, a shorter belt (52-8620-D) was installed with the pulley.
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Old 09-14-2019, 06:18 AM   #10
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Default Re: 78-8620 'A' vs 'C' gen belt 42-48

If you find an NOS belt, you may wish to hang on to it for judging purposes only then stash it away & use a "driver" belt for that purpose. You would not be the only person to practice this idea.
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Old 09-27-2019, 11:52 AM   #11
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Default Re: 78-8620 'A' vs 'C' gen belt 42-48

Thanks for the replies. Since the car, and owner, are retired from judged shows, the points issue isn't really an issue. I just wanted it correct for my own satisfaction and an answer why the Drake 'C' belt doesn't come close to fitting since this '48 has the 3-3/16 pulley and same engine as when bought new in Greeneville, MS, 2/24/48 by my grandfather. So.... on to other issues. Very grateful to ya'll.
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Old 09-27-2019, 12:05 PM   #12
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Default Re: 78-8620 'A' vs 'C' gen belt 42-48

Quote:
Originally Posted by Dunk View Post
Thanks for the replies. Since the car, and owner, are retired from judged shows, the points issue isn't really an issue. I just wanted it correct for my own satisfaction and an answer why the Drake 'C' belt doesn't come close to fitting since this '48 has the 3-3/16 pulley and same engine as when bought new in Greeneville, MS, 2/24/48 by my grandfather. So.... on to other issues. Very grateful to ya'll.
Why the Drake belt doesn't fit properly? Lack of quality control. Period - end of story.
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Old 10-03-2019, 07:10 PM   #13
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Default Re: 78-8620 'A' vs 'C' gen belt 42-48

BEST answer I've gotten as yet...
Quality Control and NOT responding to polite inquiries.....
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Old 10-06-2019, 08:51 PM   #14
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Default Re: 78-8620 'A' vs 'C' gen belt 42-48

Will either of these NOS belts work for you? They are both quite soft and flexible with no signs of cracking.
The FOMOCO belt is a molded belt with the part number, 78-8620-C1, printed on the inside of the belt. Firestone apparently was the supplier.




The second belt is a "cut" belt with the part number, 78-8620-C3, molded into the back of the belt.
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Old 10-07-2019, 09:18 AM   #15
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Default Re: 78-8620 'A' vs 'C' gen belt 42-48

I went through the same thing with my 40 with a 59 AB with the smaller pulley. After buying 3 belts that were supposed to fit two were so long that the generator was at the top of adjustment and the third was so short it would not go on. One was purchased from Drake. I finely went to the local parts store and got one that fit correctly.
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